1. Field of the Invention
The present invention relates to a corrective device for an output of an acceleration sensor that corrects an offset of the output of the acceleration sensor to a zero point and a method of correcting the output thereof.
2. Description of the Related Art
FIG. 9 is a block diagram showing a circuit configuration of the conventional corrective device for an output of the acceleration sensor disclosed in Published Unexamined Japanese Patent Application No. 5-45373.
Referring to FIG. 9, reference numeral 21 denotes a bridge of the acceleration sensor, 22 denotes an operational amplifier, 23 denotes an operational amplifier, 24 denotes a capacitor, 25 denotes a feedback resistor, each of them is a constituent of a low-pass filter. This circuit is arranged such that a time constant (T=CR) of the low-pass filter is determined by the capacitor 24 and the feedback resistor 25, and that a signal having a frequency higher than that determined on the basis of the time constant is to be attenuated. The operational amplifier 23 outputs a signal whose component is close to a direct-current component, i.e. an offset component. The output of the operational amplifier 23 is inputted to a non-inverted input terminal 26 of the operational amplifier 22, and a difference between the signal inputted to the non-inverted input terminal 26 and a signal inputted to an inverted input terminal 27 from the acceleration sensor, i.e. a corrected signal whose offset component has been removed appears at an output terminal 28 of the low-pass filter.
However, the conventional corrective device for an output of the acceleration sensor is configured by the hardware made up of circuitries, such as the operational amplifiers 22,23, the capacitor 24, and the feedback resistor 25. Therefore, the device suffers from a great change in the time constant due to dispersion of parts and is subject to restriction on the corrective ability attributable to limitations put on the parts (resistance value, capacitance value). Moreover, the hardware filter of this kind is likely to be affected by temperature and noises, and thus it is apt to lower the corrective ability due to deterioration of the parts.
The present invention has been made to solve the above problems and an object thereof is to provide a corrective device for an output of an acceleration sensor realizing an offset correction with accuracy by operation means on the software basis.
A corrective device for an output of an acceleration sensor according to the present invention includes operation processing means in control means for inputting a self-diagnosis check signal to an acceleration sensor, and executing an offset corrective operation processing of the output of the acceleration sensor prior to inputting the self-diagnosis check signal to the acceleration sensor.
According to the present invention, since the operation processing means inputs the self-diagnosis check signal to the acceleration sensor and executes an offset corrective operation processing of the output of the acceleration sensor prior to inputting the self-diagnosis check signal to the acceleration sensor, output variations due to the self-diagnosis check of the acceleration sensor are prevented from being taken in to the operation processing means. This enhances accuracy of a corrective operation processing and shortens a response time of the correction.
A method of correcting an output of an acceleration sensor according to the present invention, includes the steps of inputting a self-diagnosis check signal to the acceleration sensor by operation processing means in control means, and executing an offset corrective operation processing of an output of the acceleration sensor prior to inputting the self-diagnosis check signal to the acceleration sensor.
According to the present invention, since the method of correcting the output of the acceleration sensor includes the steps of inputting a self-diagnosis check signal to the acceleration sensor by the operation processing means in the control means, and executing an offset corrective operation processing of the output of the acceleration sensor prior to inputting the self-diagnosis check signal to the acceleration sensor, no influence is excised by the output variations due to the self-diagnosis check of the acceleration sensor. This enhances accuracy of the corrective operation and shortens a response time of the correction.
The above and other objects and the attendant advantages of the invention will become readily apparent by referring to the following detailed description when considered in conjunction with the accompanying drawings, wherein: